Within this project we intend to investigate the influence of surface roughness on erosion. To this purpose we will expose smooth metal thin films (Fe) to well characterized ion beams and measure the mass loss as function of incidence angle with a quartz micro balance for different fluence steps. The surface roughness as a function of ion fluence will be quantified with atomic force microscopy. The change in sputtering yield with increasing fluence will be measured and correlated to the change in surface roughness. For interpretation the results will be compare to SDTrimSP calculations. Due to intense plasma-wall-interaction such a surface roughening effect has to be expected under realistic reactor conditions.